U.S. Pat. No. 5,523,655 to Jennato et al. which is incorporated herein by reference describes using a neon gas discharge lamp to produce red and amber light for automotive signal lamp applications. The lamp is filled with substantially pure neon at a pressure from 20 to 200 torr. On the interior surface of the lamp envelope, there is a layer containing a phosphor which produces a green emission when stimulated. Red light is produced by operating the discharge with direct current or continuous wave alternating current power. Amber light is generated by switching the power to a pulsed mode. In the pulsed mode, certain states of neon can excite the phosphor by either ultraviolet light emission or collisional contact with the phosphor surface. The green emission from the phosphor combines with the red emission from the neon to generate amber light. By adjusting the duty cycle in the pulsed mode, the lamp can be operated to produce an amber colored light meeting the amber color coordinate requirements for automotive lighting set in the United States by the Society of Automotive Engineers (SAE) and Federal Motor Vehicle Standard 108 and in Europe by the Economic Commission for Europe (ECE). A Y.sub.3 Al.sub.5 O.sub.12 :Ce phosphor (Sylvania Type 251) is the preferred green emitting phosphor used by Jennato et al. This phosphor fluoresces with a broad emission band around 550 nm. This emission band extends below 500 nm on the blue side and above 650 nm on the red side. The combination of the green emission from this phosphor and the red emission from the neon gas produce an amber light which is acceptable for automotive applications in the United States. However, because the emission from the Y.sub.3 Al.sub.15 O.sub.12 :Ce phosphor extends below 500 nm, it is difficult to obtain an amber color within the narrower range of chromaticity values required by the ECE for European automotive lighting. Thus, it would be an advantage to provide a Y.sub.3 Al.sub.15 O.sub.12 :Ce phosphor which in combination with the red neon emission would produce more readily an acceptable amber light for European automotive applications.